linux-kernel - Re: [PATCH] dm-verity: skip verity_handle

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Message-ID: <63ce8426-8f6c-b941-822d-0437d6906f04@redhat.com>
Date: Mon, 10 Feb 2025 16:02:08 +0100 (CET)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Akilesh Kailash <akailash@...gle.com>
cc: Sami Tolvanen <samitolvanen@...gle.com>, kernel-team@...roid.com, 
    Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dm-verity: skip verity_handle_err on I/O errors for
 metadata

Hi

This doesn't seem correct - bio->bi_status is not set at a place where you 
are testing it.

If metadata I/O fails, the code goes down this branch "if (IS_ERR(data)) 
return PTR_ERR(data);" in verity_verify_level - i.e. it doesn't reach the 
piece that your patch is modifying.

I am sending a next patch (untested) that does forward error correction 
for metadata I/O failures.

Mikulas


On Sat, 8 Feb 2025, Akilesh Kailash wrote:

> Handle I/O error for metadata blocks if FEC correction fails.
> This is similar to handling I/O error for data blocks:
> 'commit 2c0468e054c0 ("dm verity: skip redundant verity_handle_err()
> on I/O errors")'
> 
> Fixes: 2c0468e054c0 ("dm verity: skip redundant verity_handle_err()
> on I/O errors")
> Signed-off-by: Akilesh Kailash <akailash@...gle.com>
> ---
> 
> Note: This patch should have been included in the data block fix patch.
> A "fixes" tag has been added to address this.
> Link: https://lore.kernel.org/all/20210913092642.3237796-1-akailash@google.com/
> ---
>  drivers/md/dm-verity-target.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index e86c1431b108..e1ce3b256f0a 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -353,16 +353,26 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
>  		} else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
>  					     hash_block, data) == 0)
>  			aux->hash_verified = 1;
> -		else if (verity_handle_err(v,
> +		else {
> +			if (bio->bi_status) {
> +				/*
> +				 * Error correction failed; Just return error
> +				 */
> +				r = -EIO;
> +				goto release_ret_r;
> +			}
> +			if (verity_handle_err(v,
>  					   DM_VERITY_BLOCK_TYPE_METADATA,
>  					   hash_block)) {
> -			struct bio *bio;
> -			io->had_mismatch = true;
> -			bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
> -			dm_audit_log_bio(DM_MSG_PREFIX, "verify-metadata", bio,
> +				struct bio *bio;
> +
> +				io->had_mismatch = true;
> +				bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
> +				dm_audit_log_bio(DM_MSG_PREFIX, "verify-metadata", bio,
>  					 block, 0);
> -			r = -EIO;
> -			goto release_ret_r;
> +				r = -EIO;
> +				goto release_ret_r;
> +			}
>  		}
>  	}
>  
> -- 
> 2.48.1.502.g6dc24dfdaf-goog
>